The invention relates to a process for the production of an unsaturated glycol diester by the reaction of a conjugated diene compound, a carboxylic acid and molecular oxygen in the presence of a solid catalyst. For example, 1,4-diacetoxy-2-butene is prepared at high conversion and high selectivity by reacting butadiene, molecular oxygen and acetic acid in the presence of a solid catalyst containing palladium, tellurium and at least one element selected from the group consisting of tin, germanium and lead. The product is an intermediate for the preparation of 1,4-butanediol.